Fixes #706: `Disjunction` as alias for `\/`
fix spurious compiler warning wrt to new tagging

AnyRef{type Tag = scalaz.Tags.Disjunction; type Self = Boolean} and Boolean are
unrelated: they will most likely never compare equal
   assert(res1.foldMap(Tags.Disjunction(_)) == false)
                                            ^

Turns out *they* do compare equal, because tags are still unboxed.